Both sides homing

Killernoy

I have a some what big printer and want the x0y0 in the middle of my printbed so I was thinking is there a way to sensorless probe the axis minimum than the maximum and set the zero point in the calculated middle?
Further information: I'm using a Ultimaker inspired printer so the head moves in x and y and the bed in z

whosrdaddy

Sensorless homing is not recommend for Z axis as it takes 4 steps to detect the stall at a reasonable speed. I use a piezo sensor on my printhead and use that for probing and Z leadscrew correction (it is an i3 clone with dual Z motors)

droftarts

You can use stall detection for homing in X and Y, see https://duet3d.dozuki.com/Wiki/Stall_detection_and_sensorless_homing
You set the bed layout with M208 (assuming v2.02 or later firmware): https://duet3d.dozuki.com/Wiki/Gcode?revisionid=HEAD#Section_M208_Set_axis_max_travel
As an example, I have a Cartesian machine set up with the bed centre as the origin, the M208 line in config.g is:

; Axis Limits
M208 X-106:114 Y-110:118 Z0:180

Ian

Killernoy

@whosrdaddy I´m using a bltouch for z

Killernoy

@droftarts what i´m asking for is that the mashine finds the bed center itself

Killernoy

@Killernoy I think of it measuring its axis travel dividing it in half and setting that as zero

whosrdaddy

@Killernoy said in Both sides homing:

is there a way to sensorless probe

BLTouch?? you asked about sensorless homing?
anyway depending on your Z axis setup this feature already available in the firmware...

fcwilt

Hi,

To put X,Y at the center of the bed is relatively easy.

One way is to determine what values of the axis min/max settings result in 0 being in the center.

If your min/max settings are not quite right you can just home using min or max and then move to the center and use G92 to declare that position to be 0.

Frederick

whosrdaddy

I think I misunderstood your question. All you need to do is set 0 as the X and Y axis minimum. Set the nozzle to the center of the bed, note the X,Y positions on DWC and enter these as axis minimum in M208. and substract the same value from the axis maximum value

Killernoy

@whosrdaddy sensorless for x and y

whosrdaddy

@Killernoy said in Both sides homing:

@whosrdaddy sensorless for x and y

ah that makes sense. Just proceed as Frederick and I explained

droftarts

what i´m asking for is that the mashine finds the bed center itself
I think of it measuring its axis travel dividing it in half and setting that as zero

Unless your printer is changing size, there's no reason to keep on recalculating this each time the printer homes; it just means that each time, especially using sensorless homing that can take up to 4 full motor steps to register, the results may be different. Just set it up once in config.g, and you don't have to worry about it. And homing won't take as long as it only has to go to one end of each axis, not both.

I seem to remember Marlin does have the functionality to have min and max homing, and it works out the axis length from this and the steps per mm, but I don't think it deduces axis home from this other than putting it at the axis minimum, and then offsetting with and M206. And I can't remember offhand the gcodes to do this, or if it's implemented in Duet firmware. The other problem would be that printers are rarely symmetrical in the X and Y axes, so even if you find the centre point for the axis travel, it's unlikely to be over the centre of the bed, so you'll still need an offset.

Ian